The roles of Ca++, cyclic nucleotides and calmodulin in the regulation of human sperm function will be studied. Such studies will focus on, 1) the interaction of these cellular messengers under conditions conducive to motility changes, capacitation, and the acrosome reaction, and 2) the targets of Ca++, cyclic nucleotide and calmodulin action in sperm. The apparent Ca++ requirement for motility maintenance and motility reactivation in sperm will be characterized and the role of cyclic nucleotides during these motility changes evaluated. The direct effects of Ca++ and cyclic nucleotides on motility reactivation and protein phosphorylation in detergent permeabilized sperm will be pursued as a correlate of the aforementioned motility studies. Incubation conditions will be defined for the synchronous induction of acrosome reactions by A-23187 in capacitated sperm. This morphological change will be quantitated using monoclonal antibodies to acrosomal antigens, and sperm cyclic nucleotide concentrations determined prior to, and during, the acrosome reaction. The enzymes of cyclic nucleotide metabolism will also be investigated. The adenylate cyclase will be characterized with special reference to its potential regulation by Ca++ and calmodulin. Properties of the cAMP dependent protein kinase will be established and the activity of this enzyme then monitored in the motility and acrosome reaction experiments. The calmodulin binding proteins of sperm and seminal plasma will be characterized with regard to identity and function. Finally, an inhibitor of the seminal plasma histone kinase will be purified and characterized with regard to both composition and biological function. Such studies should greatly aid in our understanding of the extra- and intra- cellular regulatory mechanisms controlling human sperm function and will provide a working model with which to study the biochemistry of sperm-egg interaction and the functional properties of abberant sperm populations.